The definition of a desk-based assessment given by the Institute for Archaeologists (IFA) in The Standard and Guidance for Archaeological Desk-Based Assessment (2008 Revision) is:
A programme of assessment of the known or potential archaeological resource within a specified area or site on land, inter-tidal zone or underwater. It consists of a collation of existing written, graphic, photographic and electronic information in order to identify the likely character, extent, quality and worth of the known or potential archaeological resource in a local, regional, national or international context as appropriate.
Desk-based assessments are commonly required by the local authority as part of the planning process providing a valuable insight into any heritage issues that may arise in any proposed development site.
The scope of any requested desk-based assessment will be defined by the local authority in the form of a planning condition, written specification or project design.